1. Field of the Invention
The present invention relates to a tablet liquid crystal display device, and more particularly to a tablet liquid crystal display device which senses light applied from a light irradiating device to receive an input signal applied from an exterior.
2. Description of the Prior Art
As generally known in the art, a tablet personal computer (PC) including a tablet liquid crystal display device is a PC having merits of both a notebook computer and a personal digital assistant (PDA). Such a tablet PC has the same basic structure as that of a notebook computer to enable the user to directly write, and can be assembled/disassembled to be used as a paper. The tablet liquid crystal display device of the tablet PC includes a separate reception device for receiving exterior signals, may be classified into a touch screen type device and a digitizer type device depending on input and reception methods.
In the touch screen type of tablet liquid crystal display device, a touch screen panel is attached to a front portion of the liquid crystal display device and generates a voltage or current signal corresponding to a position pressed by a user finger or a pressure transmitting device which is an input means, thereby receiving a command or information indicated by the user. A liquid crystal panel of the liquid crystal display device displays an image according to a command or information indicated by the user as described above. Meanwhile, the digitizer type of tablet liquid crystal display device has a separate antenna board attached to a rear portion of the liquid crystal display device in order to receive an input signal from an electronic pen which is an input means. Therefore, a command or information indicated by the user is inputted through the electronic pen, and a liquid crystal panel of the liquid crystal display device displays an image according to such a command or information.
From among such conventional tablet liquid crystal display devices, since the touch screen type of tablet liquid crystal display device includes a touch panel attached to the front portion of the liquid crystal display device, the permeability of the liquid crystal panel is deteriorated, so that the displayed image has a decreased luminance. Also, according to the conventional touch screen type of tablet liquid crystal display device, since the touch panel and the liquid crystal panel include a plurality of transparent layers, a light interference phenomenon may occur between the transparent layers, thereby deteriorating the image quality of the display screen. Besides, since an input signal is inputted by a user finger or the pressure transmitting device, a touch error of the user may cause a wrong operation of the tablet liquid crystal display device.
Meanwhile, in the digitizer type of tablet liquid crystal display device, since the antenna board for receiving an input signal from the electronic pen and a control panel for signal processing are separately contained, the thickness, weight and manufacturing cost of a system including the tablet liquid crystal display device increase, thereby deteriorating the value of the tablet liquid crystal display device. Also, the electromagnetic waves generated from the electronic pen may cause an image signal distortion phenomenon at an outer portion of a display area due to a metallic bezel surrounding the outline of the liquid crystal display device, thereby causing an input error and a wrong operation of the tablet PC to deteriorate the image quality of the display screen. Besides, the electromagnetic waves generated from the electronic pen and driving signals of the liquid crystal display device are interfered with each other, so that the tablet liquid crystal display device may malfunction.